Merge pull request kelvins#259 from hmigl/main

Add dynamic queue in C++

Author: kelvins

Diff for: README.md

@@ -1814,8 +1814,8 @@ In order to achieve greater coverage and encourage more people to contribute to
                 </a>
             </td>
             <td> <!-- C++ -->
-                <a href="./CONTRIBUTING.md">
-                    <img align="center" height="25" src="./logos/github.svg" />
+                <a href="./src/cpp/DynamicQueue.cpp">
+                    <img align="center" height="25" src="./logos/cplusplus.svg" />
                 </a>
             </td>
             <td> <!-- Java -->

Diff for: src/cpp/DynamicQueue.cpp

@@ -0,0 +1,93 @@
+#include <cstddef>
+#include <iostream>
+
+struct Node {
+  int key;
+  Node *next;
+
+  Node(int key) : key(key), next(nullptr) {}
+};
+
+class DynamicQueue {
+ private:
+  Node *_begin;
+  Node *_end;
+
+ public:
+  DynamicQueue() : _begin(nullptr), _end(nullptr) {}
+
+  ~DynamicQueue() {
+    while (_begin) {
+      Node *tmp = _begin;
+      _begin = _begin->next;
+      delete tmp;
+    }
+  }
+
+  bool isEmpty(void) const { return _begin == nullptr; }
+
+  void enqueue(int key) {
+    Node *node = new Node(key);
+
+    if (isEmpty()) {
+      _begin = node;
+    } else {
+      _end->next = node;
+    }
+    _end = node;
+  }
+
+  Node *dequeue(void) {
+    if (isEmpty()) {
+      return nullptr;
+    }
+
+    Node *removed = _begin;
+    _begin = _begin->next;
+    if (isEmpty()) {
+      _end = nullptr;
+    }
+    return removed;
+  }
+
+  size_t size(void) const {
+    size_t size = 0;
+
+    Node *curr = _begin;
+    while (curr) {
+      ++size;
+      curr = curr->next;
+    }
+
+    return size;
+  }
+
+  void print(void) const {
+    if (isEmpty()) {
+      std::cout << "empty queue";
+    } else {
+      Node *curr = _begin;
+      while (curr) {
+        std::cout << curr->key << ' ';
+        curr = curr->next;
+      }
+    }
+    std::cout << std::endl;
+  }
+};
+
+int main(void) {
+  DynamicQueue queue;
+
+  queue.enqueue(42);
+  queue.enqueue(5);
+  queue.enqueue(1231);
+  queue.enqueue(515);
+  queue.print();  // 42 5 1231 515
+
+  // Use 'delete' keyword to make the code leak-free
+  queue.dequeue();
+  queue.dequeue();
+  queue.print();  // 1231 515
+  return 0;
+}